Upon starvation, the rod shaped Gram-positive bacterium Bacillus subtilis can enter into differentiation process termed sporulation. Sporulation commences with an asymmetric cell division which leads to formation of two unequally sized compartments. Despite the fact that they contain the same genetic information, these compartments follow separate fates, due to dissimilar gene expression driven by compartment-specific sigma factors. While the smaller compartment, the forespore develops into heat-resistant spore, the bigger compartment, the mother cell nourishes the smaller forepore and finally lyses.
The earliest visible event in asymmetric cell division is the formation of a Z-ring by FtsZ, a tubulin like protein, and E-ring by SpoIIE at the future sporulation septum site. SpoIIE is a crucial component of the sporulation septum. SpoIIE remains at the polar septum until septum formation is complete and is later redistributed throughout the forespore membrane to perform its role in activation of the first compartment-specific sigma factor, sF. The possible third role of SpoIIE comes from the discovery that SpoIIE is subsequently recaptured at the forespore face of the polar septum where it may participate in peptidoglycan remodelling .
The rod shape of B. subtilis cells is maintained through its whole life cycle. As in most other bacteria, the cell wall is the key determinant of its cell shape. The coordinated action of two mechanisms of cell wall synthesis, one connected with cell elongation and the other with cell division seems to be responsible for rod shape maintenance .The cell elongation is driven by the actin-like homologues MreB, MreBH and Mbl. Recently, a well conserved membrane protein RodZ was discovered to be an important cell shape determinant in many bacteria .
In our previous work we have characterized RodZ protein from B. subtilis and have demonstrated that RodZ is likely an essential protein and an important part of cell shape determining network in B. subtilis . Here we examine the role of RodZ in sporulation and show that RodZ localizes to the polar septum during sporulation and co-localizes with sporulation specific SpoIIE protein. We also discovered that RodZ directly interacts with SpoIIE. We propose that RodZ is not only important cell shape determinant during vegetative growth, but is also required for asymmetric cell division which is a prerequisite of resistant spore development.
This work was supported by Grant 2/0009/13 from the Slovak Academy of Sciences.